0.0E+00

5.0E-03

1.0E-02

1.5E-02

2.0E-02

2.5E-02

350 450 550 650Temperature (K)

0.E+00

2.E-04

4.E-04

6.E-04

8.E-04

1.E-03

1.E-03

350 450 550 650

Temperature (K)

M2cdR2 advisory board, Gent, 19/06/2014

Ab initio based coverage dependent kinetics for benzene hydrogenation

a Laboratory for Chemical Technology b IFP Energies nouvelles

Technologiepark 914, 9052 Ghent, Belgium

http://www.lct.UGent.be

IFP Energies nouvelles (IFPEN)

The Fund for Scientific Research Flanders (FWO)

The STEVIN Supercomputer Infrastructure at

Ghent University, funded by Ghent University, the

Flemish Supercomputer Center (VSC), the

Hercules Foundation and the Flemish

Government – department EWI

European Research Institute of Catalysis

BP 3 - 69360 Solaize – France

http://www.ifpenergiesnouvelles.fr

* E-mail: MarieFrancoise.Reyniers@ugent.be

Stringent legislation enforce reducing aromatic concentration

Key reaction in hydrotreating to meet fuel specifications

(DE)HYDROGENATION OF AROMATICS: INDUSTRIAL AND ENVIRONMENTAL APPLICATIONS

HYDROGENATION KINETICS DEPEND ON HYDROGEN COVERAGE

CONCLUSIONS RESULTS

Periodic Density functional theory (DFT) calculations on Pd(111) Use of both functional PW91 Generalized Gradient corrected (GGA) and vdW-DF (optPBE) from Klimeš et al (2010)

MOLECULAR MODEL

MICRO-KINETIC MODEL

REACTOR MODEL

COMPUTATIONAL APPROACH MICRO-KINETIC REACTOR SIMULATIONS

Periodic DFT calculations (at different hydrogen coverage θH) are used to construct micro-kinetic models that are coupled to a CSTR reactor model to simulate catalytic activities:

Accurate theoretical simulation of hydrogenation reactions require: • Use of realistic hydrogen coverage

to calculate activation energies • Proper description of vdW

interactions to model both adsorption and surface reactions

Interplay of the kinetics for adsorption and surface reactions lead to the highest simulated activities for:

• θH = 0.11 with PW91 • θH = 0.67 with optPBE vdW-DF

vdW-DF predicts order of magnitude higher activities than GGA

ACKNOWLEDGMENTS

)( ,, freesitesCHACHAadsCHACHAdestCHA pkkcr

Gonzalo Canduela-Rodriguez a,b, M. K. Sabbe a, M. –F. Reyniers a ,*, J. –F. Joly b and G. B Marin a

vdW-DF method properly describes van der Wals interactions, and the adsorption of benzene is increased compared to PW91 by ~50 kJ mol-1

Interplay of increased surface and adsorption kinetics results in a much higher simulated activity at θH = 0.67 compared to PW91

Results in similar order of magnitude as experimental observations (0.02-10 s-1 from Chou and Vannice 1987)

Kinetics for adsorption and surface reactions are influenced by the amount of hydrogen on the surface

Ea,i

Eads,H2

Eads,B

= f(θH)

Cyclohexene and cyclohexane products are intermediates to obtain nylon polymers

Surface reaction accelerate with increasing hydrogen coverage, however, benzene adsorption on a H-covered surface strongly decreases compared than on a clean surface.

Combination of both adsorption and surface kinetics lead to maximum activities using the kinetics obtained for θH = 0.11 hydrogen coadsorbed with hydrocarbon reactants

GGA results

vdW-DF results

θH = 0

θH = 0.11

θH = 0.44

θH = 0.67

θH = 0 θH = 0.11 θH = 0.44 θH = 0.67

Activity (mmol CHA kgcat-1 s-1)

Activity (mmol CHA kgcat-1 s-1)

Ea,θ1

Ea, θ2

Ea, θ1

θH,1 θ H,2 θ H,3

BHi+θH,1

BHi+θH,2

BHi+θH,3

Vacuum layer 12 Å

Relax 2 upper layers

Fix 2 bottom layers

Artificial dipole layer